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PubMed2005

Dynamic site heterogeneity in amorphous maltose and maltitol from spectral heterogeneity in erythrosin B phosphorescence.

We have used phosphorescence from erythrosin B (tetraiodofluorescein) dispersed in thin films of either maltose or maltitol to investigate the physical properties of these amorphous pure sugar matrixes. Intensity decays collected as a function of emission wavelength over the range from 640 to 720 nm were analyzed using a stretched exponential kinetic model in which the lifetime (tau) and the stretching exponent (beta) were the physically relevant parameters. The lifetimes varied systematically with emission wavelength in both matrixes. Analysis of the temperature dependence of the lifetime at each wavelength provided an estimate of the activation energy for nonradiative quenching of the triplet state; the activation energy also varied with emission wavelength. In addition, time-resolved emission spectra exhibited a blue shift with time following excitation. These data support a photophysical model in which probes are distributed among sites that vary in terms of overall molecular mobility and in which sites with lower rates of dipolar relaxation also have lower rates of collisional quenching of the erythrosin triplet state. The amorphous matrix of both maltose and maltitol in both the glass and the melt state is thus characterized by dynamic site heterogeneity in which different sites vary in terms of their overall molecular mobility.

Erythrosine↗
PubMed2004

Determination of human complement3 by solid substrate room temperature phosphorescence immunoassay with a labelled avidin-biotin bridge.

A solid substrate room temperature phosphorescence immunoassay (SS-RTP-IA) for the determination of human complement3 (C3) based on a sandwich type assay and a labelled avidin-biotin (LAB) type assay was described. The anti-human complement3 and avidin were labeled with eosin5-isothiocyanate. On a polyamide membrane (PM), SS-RTP signals (lambda(ex)/lambda(em) = 535/678 nm) of immune complexes obtained by both assays were linear with the concentration of complement3 in the range of 6.25-100 ng/ml. The detection limits are 1.37 ng/ml for sandwich assay and 2.74 ng/ml for labeled avidin-biotin assay. (For a sample volume of 0.4 microl per spot, the mass detection limits are 0.546 and 1.09 pg/spot, respectively. If the molecular weight of human complement3 is 185,000, the detection limits are 2.95 and 5.91 amol per spot.) The results of determination of complement3 in 20 human sera obtained by labeled avidin-biotin SS-RTP-IA are correlated well with those obtained by ELISA. This study shows that SS-RTP-IA by whichever direct, sandwich or labeled avidin-biotin type assay can combine very well the characteristics of both the high sensitivity of SS-RTP and specificity of the immunoreaction.

Antibodies↗
PubMed2002

Oxyphor R2 and G2: phosphors for measuring oxygen by oxygen-dependent quenching of phosphorescence.

Oxygen-dependent quenching of phosphorescence is a useful and essentially noninvasive optical method for measuring oxygen in vivo and in vitro. Calibration of the phosphors is absolute, and once phosphors have been calibrated in one laboratory the same constants can be used by anyone else as long as the measurement is done under the same conditions. Two new phosphors, one based on Pd-meso-tetra-(4-carboxyphenyl)porphyrin and the other on Pd-meso-tetra-(4-carboxyphenyl)tetrabenzoporphyrin, are very well suited to in vivo oxygen measurements. Both phosphors are Generation 2 polyglutamic Pd-porphyrin-dendrimers, bearing 16 carboxylate groups on the outer layer. These phosphors are designated Oxyphor R2 and Oxyphor G2, respectively. Both are highly soluble in biological fluids such as blood plasma and their ability to penetrate biological membranes is very low. The maxima in the absorption spectra are at 415 and 524 nm for Oxyphor R2 and 440 and 632 nm for Oxyphor G2, while emissions are near 700 and 800 nm, respectively. The calibration constants of the phosphors are essentially independent of pH in the physiological range (6.4 to 7.8). In vivo application is demonstrated by using Oxyphor G2 to noninvasively determine the oxygen distribution in a subcutaneous tumor growing in rats.

Animals↗
PubMed2001

The conformation of serum albumin in solution: a combined phosphorescence depolarization-hydrodynamic modeling study.

There is a striking disparity between the heart-shaped structure of human serum albumin (HSA) observed in single crystals and the elongated ellipsoid model used for decades to interpret the protein solution hydrodynamics at neutral pH. These two contrasting views could be reconciled if the protein were flexible enough to change its conformation in solution from that found in the crystal. To investigate this possibility we recorded the rotational motions in real time of an erythrosin-bovine serum albumin complex (Er-BSA) over an extended time range, using phosphorescence depolarization techniques. These measurements are consistent with the absence of independent motions of large protein segments in solution, in the time range from nanoseconds to fractions of milliseconds, and give a single rotational correlation time phi(BSA, 1 cP, 20 degrees C) = 40 +/- 2 ns. In addition, we report a detailed analysis of the protein hydrodynamics based on two bead-modeling methods. In the first, BSA was modeled as a triangular prismatic shell with optimized dimensions of 84 x 84 x 84 x 31.5 A, whereas in the second, the atomic-level structure of HSA obtained from crystallographic data was used to build a much more refined rough-shell model. In both cases, the predicted and experimental rotational diffusion rate and other hydrodynamic parameters were in good agreement. Therefore, the overall conformation in neutral solution of BSA, as of HSA, should be rigid, in the sense indicated above, and very similar to the heart-shaped structure observed in HSA crystals.

Animals↗
PubMed1976

A study of solvent effects on the phosphorescence properties of flavins.

A combination of zero field triplet state techniques are used to study the excited electronic states of a series of flavin and flavin related molecules both in single crystals and glass matrices. Particular attention is given to the effects of solvent interaction on the triplet state properties of the flavin molecules. The total phosphorescence decay rate constants at 1.4 degrees K are reported for the flavin molecules in polar and nonpolar solvents. The rate constants are then correlated to the degree of solvent interaction. Results indicate possible complex formation between the isoalloxazine and adenine groups in FAD. Finally, the results and possible interpretation on the study of a flavoenzyme, L-amino acid oxidase are presented.

Amino Acid Oxidoreductases↗
PubMed1983

Singular oxygen effects on the room-temperature phosphorescence of alcohol dehydrogenase from horse liver.

The room-temperature phosphorescence of alcohol dehydrogenase from horse liver in the presence of oxygen has the characteristics of a light-induced emission as it appears only after a certain amount of excitation has been absorbed. The initial lag period, the steady-state intensity, and the duration of the induced state are dominated by the oxygen content of the solution, the rate of light absorption, and the radiation dose. The phenomenon is not unique to this enzyme and the data are consistent with photochemical depletion of oxygen.

Alcohol Dehydrogenase↗
PubMed1986

Gated quenching of intrinsic fluorescence and phosphorescence of globular proteins. An extended model.

We present a theoretical model to account for the quenching data of macromolecular fluorescence and phosphorescence when the accessibility to the quencher is gated by a dynamic mechanism coupled to the fluctuation of the macromolecular matrix. We show that the model currently in use to interpret gated quenching processes gives only approximate results in both qualitative and quantitative terms, and it can be regarded as a specific case of the presented model. We show that the gating dynamics affect both the apparent accessibility (alpha obs) and Ksv values obtained by the modified Stern-Volmer plot. The effect of gating on alpha obs and Ksv depends upon the relative rate of gating compared to the excited state lifetime. The model allows us to predict the effect of viscosity on quenching if it takes place by a gated mechanism. The prediction can and is, in this case, compared to the existing data on glycerol effects on acrylamide quenching of the tryptophan fluorescence in RNAse T1. The result shows that a simple gated model is not compatible with the observed quenching behavior.

Kinetics↗
PubMed1987

Quenching of alkaline phosphatase phosphorescence by O2 and NO. Evidence for inflexible regions of protein structure.

The rate constant for quenching the phosphorescence of alkaline phosphatase by molecular oxygen was measured as a function of temperature. The results disagree with previous determinations and, contrary to fluorescence quenching, show that diffusion of O2 to this region of the macromolecule is a highly hindered process. When nitric oxide is introduced as a quencher, similarly small rate constants were found. While the activation energy for this process is identical for both quenchers, it is much smaller than for structural fluctuations at the chromophore site as manifested by the intrinsic triplet-state lifetime. These findings are analyzed in terms of a mechanism that takes into account static quenching at large distances and does not require penetration of the quencher all the way to the chromophore.

Alkaline Phosphatase↗
PubMed1997

The influence of intraocular pressure and systemic oxygen tension on the intravascular pO2 of the pig retina as measured with phosphorescence imaging.

The intravascular oxygen tension (pO2) of the pig retina was determined by measuring the phosphorescence lifetime of an intravenously injected dye. Pseudocolor images of the intravascular retinal pO2 were obtained. The method is noninvasive except for the application of the dye. The measurement system was adapted to a fundus camera. The systemic arterial oxygen pressure (PaO2) as well as the intraocular pressure (IOP) were altered. In the measurements the pO2 of the choriocapillaris was close to the systemic PaO2. Under normoxia, the retinal veins showed a lower pO2 of about 40 mm Hg. We found evidence of an autoregulation of the retinochoroidal pO2. The retina and the optic nerve head showed an autoregulation of the intravascular pO2 at low IOP, but were more sensitive to a moderate elevation of the IOP of about 40 mm Hg, as compared to the choroidal pO2. The pO2 of the choriocapillaris seemed to change little until the considerably high IOP value of about 50 mm Hg was attained. This behavior is due to either the high perfusion reserve capacity of the choroid or to autoregulation. Although our experiments refer to the perfusion of the pig eye, the results provide indirect evidence that even during a glaucoma attack the human choroid might be able to maintain a reasonable oxygen supply to the retina, whereas the intravascular pO2 of the retinal vessels and of the optic nerve head decrease strongly. The adaptation to a fundus camera facilitates a future clinical application if a nontoxic dye can be developed.

Animals↗
PubMed2002

Direct detection of singlet oxygen via its phosphorescence from cellular and fungal cultures.

In summary, we have developed methods to detect 1O2 spectrally from viable keratinocytes and fungal mycelial cultures. Both time-resolved and steady-state spectrophotometers were used, providing complementary information on optimal conditions for the unambiguous detection of 1O2 phosphorescence. By using our techniques, we were able to confirm that photosensitizers in contact with living cells indeed generate 1O2. The model systems and the procedures described can be adopted for other studies involving 1O2 and oxidative stress in living cells.

Ascomycota↗
PubMed2000

Optimal sample preparation conditions for the determination of uranium in biological samples by kinetic phosphorescence analysis (KPA).

Kinetic phosphorescence analysis (KPA) is a proven technique for rapid, precise, and accurate determination of uranium in aqueous solutions. Uranium analysis of biological samples require dry-ashing in a muffle furnace between 400 and 600 degrees C followed by wet-ashing with concentrated nitric acid and hydrogen peroxide to digest the organic component in the sample that interferes with uranium determination by KPA. The optimal dry-ashing temperature was determined to be 450 degrees C. At dry-ashing temperatures greater than 450 degrees C, uranium loss was attributed to vaporization. High temperatures also caused increased background values that were attributed to uranium leaching from the glass vials. Dry-ashing temperatures less than 450 degrees C result in the samples needing additional wet-ashing steps. The recovery of uranium in urine samples was 99.2+/-4.02% between spiked concentrations of 1.98-1980 ng (0.198-198 microg l(-1)) uranium, whereas the recovery in whole blood was 89.9+/-7.33% between the same spiked concentrations. The limit of quantification in which uranium in urine and blood could be accurately measured above the background was determined to be 0.05 and 0.6 microg l(-1), respectively.

Humans↗
PubMed2003

Determination of allopurinol by micelle-stabilised room-temperature phosphorescence in real samples.

A very simple, rapid and highly sensitive method has been developed for the determination of allopurinol. The method is based on the room temperature phosphorescence of allopurinol in sodium dodecylsulphate (SDS) micelles, with thallium (I) providing the external heavy atom and sodium sulphite acting as the oxygen scavenger. Under the optimum experimental conditions, the range of application is 0.25-7.0 microg ml(-1) and the limit of detection is 0.014 microg ml(-1). The most relevant characteristic of this method is its great selectivity, e.g. allopurinol can be determined in the presence of its metabolite, oxypurinol. The results of the analysis of several pharmaceutical preparations were satisfactory. The clinical applicability of this procedure has been tested by analysing allopurinol in urine samples.

Allopurinol↗
PubMed1997

A sensitive method for the determination of uranium in biological samples utilizing kinetic phosphorescence analysis (KPA).

Kinetic phosphorescence analysis is a technique that provides rapid, precise and accurate determination of uranium concentration in aqueous solutions. This technique utilizes a laser source to excite an aqueous solution of uranium, and measures the emission luminescence intensity over time to determine the luminescence decay profile. The lifetime of the luminescence decay profile and the linearity of the log luminescence intensity versus time profile are indications of the specificity of the technique for uranium determination. The luminescence intensity at the onset of decay (the initial luminescence intensity), which is the luminescence intensity at time zero after termination of the laser pulse used for excitation, is proportional to the uranium concentration in the sample. Calibration standards of known uranium concentrations are used to construct the calibration curve between the initial luminescence intensity and uranium concentration. This calibration curve is used to determine the uranium concentration of unknown samples from their initial luminescence intensity. We developed the sample preparation method that allows the determination of uranium concentrations in urine, plasma, kidney, liver, bone spleen and soft tissue samples. Tissue samples are subjected to dry-ashing in a muffle furnace at 600 degrees C and wet-ashing with concentrated nitric acid and hydrogen peroxide twice to destroy the organic component in the sample that may interfere with uranium determination by KPA. Samples are then solubilized in 0.82 M nitric acid prior to analysis by KPA. The assay calibration curves are linear and cover the range of uranium concentrations between 0.05 micrograms l-1 and 1000 micrograms l-1 (0.05-1000 ppb). The developed sample preparation procedures coupled with the KPA technique provide a specific, sensitive, precise and accurate method for the determination of uranium concentration in tissue samples. This method was used to quantify uranium in different tissue samples obtained over a period of 90 days following a single intraperitoneal uranium dose of 0.1 mg kg-1 in rats.

Animals↗
PubMed1997

Dynamic and thermodynamic effects of glycerol on bovine serum albumin in aqueous solution: a tryptophan phosphorescence study.

The phosphorescence decay of bovine serum albumin in water-glycerol solutions at room temperature is analysed by the maximum entropy method. While in pure water the decay was found to be quasi-monoexponential, in water-glycerol mixtures it is associated with more complex lifetime distributions. This is a direct proof for the existence of multiple protein conformers. It was also found that the increase of the glycerol concentration induces a continuous shift of the lifetime pattern to longer lifetimes. This effect is analysed in connection with the coupling between the solvent viscosity and the internal protein mobility.

Animals↗
PubMed2003

Phosphorescence spectra and triplet state lifetimes of palladium octaethylporphyrin, palladium octaethylchlorin and palladium 2,3-dimethyloctaethylisobacteriochlorin at 77 K.

The phosphorescence spectra and triplet state lifetimes of palladium octaethylporphyrin (PdOEP), palladium octaethylchlorin (PdOEC) and palladium 2,3-dimethyloctaethylisobacteriochlorin (PdOEiBC) in n-octane Shpolskii matrices at 77 K are reported. The lifetime and T(1)/S(0) origin energy of each complex are: PdOEP, 1.90+/-0.04 ms, 15162 cm(-1); PdOEC, 0.43+/-0.03 ms, 12547 cm(-1) and PdOEiBC, 0.59+/-0.03 ms, 12863 cm(-1).

Luminescence↗
PubMed2003

Study on the paper substrate room temperature phosphorescence of theobromine, caffeine and theophylline and analytical application.

Paper substrate room temperature phosphorescence (RTP) of theobromine (TB), caffeine (CF) and theophylline (TP) were investigated. The method is based on fast speed quantitative filter paper as substrate and KI-NaAc as heavy atom perturber. Various factors affecting their RTP were discussed in detail. Under the optimum experimental conditions, the linear dynamic range, limit of detection (LOD), and relative standard deviation (R.S.D.) were 14.41 approximately 576.54 ng per spot, 1.14 ng per spot, 4.8% for TB, 5.44 approximately 699.08 ng per spot, 0.78 ng per spot, 1.56% for CF, 7.21 approximately 360.34 ng per spot, 1.80 ng per spot, 3.80% for TP, respectively. The first analytical application for the determination of these compounds was developed. The recovery of standard samples added to commercial products chocolate, tea, coffee and aminophylline is in the range 92.80-106.08%. The proposed method was successfully applied to real sample analysis without separation.

Aminophylline↗
PubMed2002

Quenched phosphorescence detection in cyclodextrin-based electrokinetic chromatography.

Quenched phosphorescence detection is a sensitive detection method recently introduced in capillary zone electrophoresis. It is based on the dynamic quenching interaction of the analytes (quenchers) with a phosphorophore, 1-bromo-4-naphthalenesulfonate (BrNS), present in the separation buffer. In this study, it is shown that this detection method can also be used in cyclodextrin-based electrokinetic chromatography (CD-EKC) despite the presence in the buffer solution of cyclodextrins, which are known to reduce the luminescence quenching rate constants. Experiments indicate that BrNS mainly resides in the aqueous phase, while the analytes are distributed between both phases. In principle, the observed quenching might arise from the interaction of BrNS with uncomplexed as well as complexed analytes. However, from the dependence of the fractional quenching on the capacity factor (the normalized fractional quenching was found to be equal to the fraction of analyte in the aqueous phase), it was concluded that only aqueous-phase quenching contributes significantly to the observed quenching. Nevertheless, separation and detection can be regarded as fully compatible, because the capacity factors encountered in CD-EKC are generally low (in this study they ranged from about 0.1 to 2.5). Indeed, with nitroaromatic compounds as the target analytes, limits of detection in the 10(-8) M range were achieved.

Journal Article↗